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Low-mode internal tide generation by topography: an experimental and numerical investigation

Published online by Cambridge University Press:  25 September 2009

PAULA ECHEVERRI ,
M. R. FLYNN ,
KRAIG B. WINTERS  and
THOMAS PEACOCK
PAULA ECHEVERRI*
Affiliation:
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
M. R. FLYNN
Affiliation:
Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
KRAIG B. WINTERS
Affiliation:
Scripps Institution of Oceanography and Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093, USA
THOMAS PEACOCK
Affiliation:
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
*
†Email address for correspondence: paulae@mit.edu
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Abstract

We analyse the low-mode structure of internal tides generated in laboratory experiments and numerical simulations by a two-dimensional ridge in a channel of finite depth. The height of the ridge is approximately half of the channel depth and the regimes considered span sub- to supercritical topography. For small tidal excursions, of the order of 1% of the topographic width, our results agree well with linear theory. For larger tidal excursions, up to 15% of the topographic width, we find that the scaled mode 1 conversion rate decreases by less than 15%, in spite of nonlinear phenomena that break down the familiar wave-beam structure and generate harmonics and inter-harmonics. Modes two and three, however, are more strongly affected. For this topographic configuration, most of the linear baroclinic energy flux is associated with the mode 1 tide, so our experiments reveal that nonlinear behaviour does not significantly affect the barotropic to baroclinic energy conversion in this regime, which is relevant to large-scale ocean ridges. This may not be the case, however, for smaller scale ridges that generate a response dominated by higher modes.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 636 , 10 October 2009 , pp. 91 - 108
Copyright
Copyright © Cambridge University Press 2009

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Footnotes

‡

Present address: Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada T6G 2G8.

References

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